MDSTKLUS LJ:VIS. 165 



then laterally and backward, and separates into two parts — 

 one of which continues backward and innervates organs 

 77 and 78 infra-orbital, the other turning forward and 

 innervating organs 75 and 76. Tlie distal one of the two 

 branches continues still farther forward, and, branching, 

 innervates organs 70 to 74. Each of these two buccal is 

 branches is closely accompanied, through a part of its 

 course, by a general sensory branch of the ramus maxillaris. 



Anterior to these last two branches the buccalis turns 

 downward, with the maxillaris trigeraini, on to the lateral 

 surface of the muscle Add/3, and there immediately gives 

 off a large branch which, breaking up into several smaller 

 branches, is distributed entirely to the sensory organs of 

 the large buccal group of ampullae. The several branches 

 of this large ampullary branch are grouped into two por- 

 tions, rather than forming parts of two main branches. The 

 branches of the larger one of these two portions go to 

 ampullae that lie dorsal to a membrane that extends inward 

 from the internal surface of that section of the infra-orbital 

 canal that lies between the suborbital bend in the canal and 

 the point where the hyomandibular canal is given off, the 

 branches of the other portion going to ampullae that lie 

 ventro-mesial to the same membrane. The membrane and 

 nerves thus here indicate two sub-groups of this large group 

 of ampuUee, and they may, possibly, correspond to the inner 

 and outer buccal groups of Ewart's descriptions. It is, 

 however, to be remembered that neither of the sub-groups 

 of Mustelus occupies the position of Ewart's inner buccal 

 group, that position seeming to correspond exactly to that 

 occupied by my deep group of ophthalmic ampullae. 



As this large ampullary nerve is given off by the buccalis, 

 the remaining fibres of the nerve, which are now entirely 

 lateral sensory ones, separate into two principal portions. 

 One of these portions separates almost immediately into 

 several branches, all of which run outward, forward, and 

 downward, and supply organs 46 to 69 infra-orbital, these 

 organs all lying in the three arms of the double suborbital 



